Cut the pork into bite-sized pieces and thinly slice the onion and green onion.
In a bowl, mix together gochujang, red pepper powder, soy sauce, minced garlic, erythritol, pepper, and sesame oil to make the sauce.
Add the sauce to the pork and marinate for 10 minutes.
Heat cooking oil in a pan and fry the green onion first to bring out its aroma.
Add the pork and stir-fry over medium heat, then add the onion and stir-fry together.
Once the meat is fully cooked, turn off the heat and serve on a plate.